This invention relates to an impact wrench. In particular, the invention concerns an impact wrench for use with a variety of nuts and bolts.
There are many types of wrenches for gripping and turning nuts and bolts. However, where the nut or bolt being turned is attached to another member which may itself turn when the nut or bolt is being turned by the wrench, it is generally necessary to hold the other member fast in order to turn the nut or bolt, otherwise the other member and nut or bolt will turn in unison.
Where it is readily possible to hold the other member fast by means such as another wrench, such situations do not present a problem. However, there are occasions when this is not easily achievable, for example, in a car engine, the front pulley is generally bolted onto a rotatable shaft which is not readily accessible for holding fast against rotation. Furthermore, in some cars, there may not be a great deal of clearance between the nut or bolt attaching the pulley, the radiator, the engine bay or other engine components, thereby leaving little room to remove the nut or bolt.
Thus there is a need in some situations for a wrench design which can be used in confined spaces. Furthermore, there is a need for a wrench design which can be used to loosen members such as nuts or bolts even though they are attached to other members which may be rotatable with the nut or bolt.
It is an object of the invention to provide an impact wrench that meets at least one of the needs referred to above.
According to the present invention there is provided an impact wrench having:
a handle having an impact surface;
an arm pivotally connected to the handle and of unitary construction with the handle; and
a key or a keyseat on the arm for coupling with a respective key or keyseat of a wrench tool, wherein the wrench tool may rotate a nut or bolt when the impact surface is impacted upon.
The unitary construction enables the impact wrench to be used in confined spaces without the problem of the arm detaching from the handle by accident.
Preferably, the key or keyseat enables the coupling of different wrench tools to the arm. The coupling may be magnetised.
In one form of the invention, the arm may have a keyseat for receiving a key of a wrench tool. For instance, the keyseat may have an aperture into which is insertable a like-shaped key of a wrench tool.
In another form of the invention, the arm may have a key extending laterally from one or both sides of the arm and the key may be receivable within a like-shaped keyseat of a wrench tool. The key may, for instance, have a rectangular body extending from both sides of the arm.
Preferably, the arm and the handle pivot beside one another in spaced parallel planes, and the arm may be pivoted relative to the handle through an arc of at least 60 degrees. More preferably, the arm is pivotable relative to the handle through an arc of at least 240 degrees. If the arm does not have a key or keyseat extending therefrom in an obstructive manner, then the arm may be pivotable through one or more complete revolutions relative to the handle. This enables the impact wrench to not only loosen a nut or bolt, but to also unscrew the nut or bolt completely.
The arm may be pivotally connected to the handle with a rivet, a pin, a nut and bolt combination, or using any suitable means known to persons skilled in the art.
The handle and arm may comprise any suitable material or materials which can withstand an impact from a member such as a hammer. Steel is a material which is suitable, particularly steel in alloy form, eg. chrome or molybdenum alloy.
Preferably, the impact surface is located at an end of the handle and remote from the pivotal connection with the arm. Preferably, the impact surface includes an impact-resistant cap. The cap may comprise any suitable material, such as metal or plastics material, The cap may be a separate component or it may be an integral part of the handle. If desired, the cap may have a grip that encompasses an upper end of the handle. The cap may have a circumferential flange for shielding the user""s hand from a misdirected hammer blow.
In a preferred form of the invention, the impact wrench includes a wrench tool coupled to the key or keyseat on the arm. The wrench tool may comprise any suitable tool for engaging a nut or bolt. The wrench tool may comprise, for instance, an open end of a spanner, a ring spanner, or a socket of a socket wrench. Preferably, the wrench tool comprises a socket of a socket wrench.
In another aspect of the invention, there is provided a method of loosening a first member from a second member held to the first member in a manner which allows the two to rotate together, said method comprising loosening the first member by rotation with respect to the second member by using an impact wrench as hereinbefore described and applying a blow to the impact surface of the impact wrench.